Triphenylene based aromatic compounds and OLEDs utilizing the same

ABSTRACT

Disclosed is a triphenylene based aromatic compound, wherein a benzene center is substituted with a triphenylene group and another aromatic group such as triphenylenyl, pyrenyl, phenylvinyl, carbazolylphenyl, or arylanthryl in the meta position of the benzene center. The meta-substituted aromatic compound of the invention has better thermal stability (Tg) than the conventional para-substituted aromatic compound. The meta-substituted aromatic compound, served as a hole transporting layer or a host material applied in a light emitting layer in an OLED, is more preferable than the conventional para-substituted aromatic compound.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a triphenylene based aromatic compound,and in particular relates to an organic light emitting diode utilizingthe same.

2. Description of the Related Art

The earliest report of organic electroluminescence was made by Pope etal in 1963, who observed a blue fluorescence from 10-20 μm ofcrystalline anthracene by applying voltage across opposite sides of thecrystal. Thus, starting a wave of first improvements in organicelectroluminescence research. However, difficulties of growing largeareas of crystals were a challenge. The driving voltage of the devicewas too high and the efficiency of organic materials was lower thaninorganic material. Because of the disadvantages of the devices, thedevices were not widely applied due to practical purposes.

However, a major development in organic electroluminescence technologywas reported in 1987. Tang and VanSlyke of Eastman Kodak Company usedvacuum vapor deposition and novel hetero junction techniques to preparea multilayered device with hole/electron transporting layers.4,4-(cyclohexane-1,1-diyl)bis(N,N-dip-tolylbenzenamine) (TPAC) was usedas a hole transporting layer, and Alq₃ (tris(8-hydroxyquinolinato)aluminum(III)) film with good film-forming properties was used as anelectron transporting and emitting layer. A 60-70 nm-thick film wasdeposited by vacuum vapor deposition with a low-work function Mg:Agalloy as a cathode for efficient electron and hole injections. Thebi-organic-layer structure allowed the holes and electrons to recombineat the p-n interface and then emit light. The device emitted green lightof 520 nm, and was characterized by low driving voltage (<10 V), highquantum efficiency (>1%) and good stability. The improvements, onceagain, arouse interest in organic electroluminescence research.

Meanwhile, Calvendisg and Burroughes et al. at Cambridge University in1990 was the first to report using conjugated polymer PPV(poly(phenylene vinylene)) as an emitting layer in a single-layereddevice structure by solution spin coating. The development of anemitting layer with conjugated polymer drew great interest and quicklysparked research due to the simplicity of fabrication, good mechanicalproperties of polymer, and semiconductor-like properties. In addition, alarge number of organic polymers are known to have high fluorescenceefficiencies.

In U.S. patent application Ser. No. 11/968,353, the inventor of theinvention had disclosed the triphenylene derivatives application in bluelight emitting device. In previously application, the aromatic centerhad two substituents such as triphenylenyl group, pyrenyl group, orcombinations thereof. When the aromatic center was benzene, the twosubstituents were para-substituted on the benzene. This application onlyfocused on tuning the center aromatic types, however, it did notdisclose the different substituted positions of the substituents and theinfluences thereof.

Accordingly, methods and corresponding formulae are called for to reducethe symmetry of the triphenylene based aromatic compound. In addition,the methods without largely changing the synthetic steps and thecorresponding formulae may enhance the thermal stability (such as Tg)and luminescence property (such as external quantum efficiency) of thedevice utilizing the triphenylene based aromatic compound.

BRIEF SUMMARY OF THE INVENTION

The invention provides a triphenylene based aromatic compound, having ageneral formula:

wherein Ar₁ is a triphenylenyl group; Ar₂ is a triphenylenyl group, apyrenyl group, a phenylvinyl group, a carbazolylphenyl group, or anarylanthryl group.

The invention also provides an organic light emitting diode, comprising:an anode; a cathode; and an organic layer disposed between the anode andthe cathode, wherein the organic layer comprises the describedtriphenylene based aromatic compound.

A detailed description is given in the following embodiments.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

The invention provides triphenylene based aromatic compounds serving asa hole transporting layer or a host material in a light emitting layerof OLEDs. Because the triphenylene based aromatic compounds haveexcellent thermal stability and luminescence efficiency, they mayfurther enhance the brightness, the external quantum efficiency, thecurrent efficiency, and the power efficiency of a device utilizing thesame.

The triphenylene based aromatic compounds are synthesized as below. Whenboth of the two meta-substituted groups of the compound are thetriphenylenyl groups, the compound can be synthesized as shown inFormula 1:

The synthesis of the starting material A in Formula 1 is disclosed inU.S. patent application Ser. No. 11/968,353 and thus is omitted here.

When the two meta-substituted groups of the compound are a triphenylenylgroup and another aromatic group, respectively, the compound can besynthesized by Formula 2, followed by Formula 3 (Suzuki coupling).

The Ar₂ in Formula 3 is an aromatic group such as a triphenylenyl group,pyrenyl group, a phenylvinyl group, a carbazolylphenyl group, or anarylanthryl group. In one embodiment, the arylanthryl group includespyridinylanthryl group, a phenylanthryl group, a naphthenylanthrylgroup, a biphenylanthryl group, or a carbazolylanthryl group Theboron-containing starting material is prepared by following steps.n-BuLi is added to an aromatic bromide for metal-halogen exchange. Theboron agent and the HCl/pinacol are sequentially added to the resultingof the metal-halogen exchange, thereby forming boric acid or boricester.

In one embodiment, the triphenylenyl group, Ar₂, and a benzene center ofthe triphenylene based aromatic compound independently have one or moresubstituents selected from the group consisting of hydrogen, halogen,aryl, halogen-substituted aryl, halogen-substituted aryl alkyl,haloalkyl-substituted aryl, haloalkyl-substituted aryl alkyl,aryl-substituted C₁₋₂₀ alkyl, electron donating group, electronwithdrawing group, and heterocyclic-substituents. The electron donatinggroup includes a C₁₋₂₀ alkyl group, a C₁₋₂₀ alkoxyl group, a C₁₋₂₀ alkylamino group, or an aryl amino group. The electron withdrawing groupincludes a nitrile group, a nitro group, a carbonyl group, a cyanogroup, or a halogenated C₁₋₂₀ alkyl group.

The invention further provides an organic light emitting diode (OLED),including an anode, a cathode, and a light emitting layer disposedbetween the anode and the cathode, wherein the light emitting layerincludes the described triphenylene based aromatic compound. The anodeincludes indium tin oxide, indium zinc oxide, aluminum zinc oxide, orcombinations thereof. The anode can be formed by evaporation orsputtering. The cathode includes inorganic conductive material such asmagnesium silver alloy, calcium, lithium fluoride, aluminum, orcombinations thereof. The cathode can be formed by evaporation orsputtering. In one embodiment, a hole injecting layer, a holetransporting layer, and/or other suitable layered materials can bedisposed between the light emitting layer and the anode. The holeinjecting layer includes molybdenum trioxide, copper phthalocyanine,poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS),N,N′-di-phenyl-N,N′-di-[4-(N,N-di-phenyl-amino)phenyl]benzidine (NPNPB)and 4,4′,4″-tris(N-3-methylphenyl-N-phenyl-amino)-triphenylamine(m-TDATA). The hole transporting layer includes4′4′,4″-tris(carbazol-9-yl)-triphenylamine (TCTA),N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl)-4,4′-diamine(TPD), or N,N′-bis(1-naphyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine(NPB).

In one embodiment, an electron injecting layer, an electron transportinglayer, an electron blocking layer, and/or other suitable layeredmaterials can be disposed between the light emitting layer and thecathode. The electron injecting layer includes alkali halide,alkaline-earth halide, alkali oxide, or alkali carbonate, such as LiF,CsF, NaF, CaF₂, Li₂O, Cs₂O, Na₂O, Li₂CO₃, Cs₂CO₃, or Na₂CO₃. Theelectron transporting layer includes tris(8-hydroxy quinoline) aluminum(Alq3) or 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)(TPBI). The hole blocking layer includes2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), aluminum (III)bis(2-methyl-8-quninolinato)-4-phenylphenolate (BAlq),bis(10-hydroxybenzo[h]qinolinato) beryllium (BeBq2) or2,2′,2″-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBI).

The light emitting layer may be further doped with other dopants such asBCzVBi as shown in Formula 4. As such, the luminescence efficiency ofthe OLED is enhanced by the host-guest system.

In another embodiment, other conventional host materials and dopants areselected as be the light emitting layer of the OLED, and the describedtriphenylene based aromatic compounds may serve as the hole transportinglayer of the OLED. Because the triphenylene based aromatic compounds ofthe invention have low HOMO value, thereby efficiently transporting thehole. In addition, the material and the formation of the other layeredstructures such as the cathode, the electron injecting layer, theelectron transporting layer, the hole blocking layer, the hole injectinglayer, and the anode can be similar to that which was previouslydescribed.

EXAMPLES Example 1

As shown in Formula 1, the compound A (1.00 g, 4.1 mmol),1.3-diiodobenzene (0.63 g, 1.9 mmol), zinc (2.69 g, 41.4 mmol), andPdCl₂(PPh₃)₂ (0.44 g, 0.6 mmol) were charged in a two-necked bottle. Thebottle was then vacuumed and purged with nitrogen, and dried toluene (88mL) and triethyl amine (5.75 mL, 41.5 mmol) were added to the bottle.The mixture in the bottle was heated to 100° C. for reaction for 24hours, and the resulting was filtered to remove metal. The filtrate wascondensed to remove the solvent, and then purified by chromatographywith an eluent of dichloromethane/n-hexane (1:6) to obtain a product.The product was sublimated at a temperature of 305° C. to obtain a whitesolid of 0.57 g (yield=56%).

The white solid product in Formula 1 was dissolved in dichloromethane toform a solution having a concentration of 10⁻⁵M, or evaporated to form afilm having a thickness of 30 nm. The absorption-emission peaks of thefilm and the solution are tabulated in Table 1.

The spectra data of the product in Formula 1 is shown as follows. ¹H NMR(400 MHz, CDCl₃): δ 9.02 (s, 2H), 8.85-8.81 (m, 4H), 8.75-8.70 (m, 6H),8.30 (s, 1H), 8.08 (dd, J=8.6, 1.6 Hz, 2H), 7.92 (dd, J=8.6, 1.6 Hz,2H), 7.75-7.71 (m, 9H). ¹³C NMR (125 MHz, CDCl₃): δ 142.8, 140.9, 131.2,131.1, 130.9, 130.6, 130.2, 130.1, 128.2, 128.1, 128.1, 127.4, 127.3,124.9, 124.5, 124.3, 124.3, 122.7. HRMS (m/z): [M⁺] calculated forC₄₂H₂₆: 530.2035. found: 530.2034. Element Analysis: calculated forC₄₂H₂₆: C, 95.06; H, 4.94. found: C, 94.82; H, 4.90.

Example 2

As shown in Formula 2, compound A (4.00 g, 16.4 mmol), zinc (10.72 g,163.9 mmol), and PdCl₂(PPh₃)₂ (1.16 g, 1.7 mmol) were charged in atwo-necked bottle. The bottle was then vacuumed and purged withnitrogen, and dried toluene (350 mL), 1-bromo-3-iodobenzene (2.08 mL,16.4 mmol), and triethyl amine (5.75 mL, 41.5 mmol) were added to thebottle. The mixture in the bottle was heated to 100° C. for reaction for24 hours, and the resulting was filtered to remove metal. The filtratewas condensed to remove the solvent, and then purified by chromatographywith an eluent of n-hexane to obtain a white solid of 3.42 g(yield=54%). The white solid product in Formula 2 was dissolved indichloromethane to form a solution having a concentration of 10⁻⁵M, orevaporated to form a film having a thickness of 50 nm. Theabsorption-emission peaks of the film and the solution are tabulated inTable 1.

The spectra data of the product in Formula 2 is shown as follows. ¹H NMR(400 MHz, CDCl₃): δ 8.79 (s, 1H), 8.74-8.64 (m, 5H), 7.93 (s, 1H), 7.83(d, J=8.4 Hz, 1H), 7.72-7.66 (m, 5H), 7.53 (d, J=7.6 Hz, 1H), 7.38 (t,J=7.6 Hz, 1H). ¹³C NMR (125 MHz, CDCl₃): δ 143.2, 138.2, 130.4, 130.3,130.0, 130.0, 129.8, 129.5, 129.4, 129.3, 128.3, 127.4, 127.4, 127.3,127.3, 126.0, 126.0, 124.0, 123.3, 123.3, 123.3, 123.0, 121.7. HRMS(m/z): [M⁺] calculated for C₂₄H₁₅Br, 382.0357. found, 382.0352.

As shown in Formula 3, the product in Formula 2 (1.00 g, 2.6 mmol),pyren-1-ylboronic acid (0.64 g, 2.6 mmol, synthesized by Example 2 inU.S. patent application Ser. No. 11/968,353), potassium carbonatesolution (2.0 M, 6.50 mL), and dried toluene (27 mL) were charged in atwo-necked bottle. The bottle was deoxygenated and purged with nitrogen,and the mixture in the bottle was stirred at 60° C. until it was totallydissolved. The nitrogen pressure of the bottle was increased, andPd(PPh₃)₄ (0.15 g, 0.1 mmol) was rapidly added into the bottle. Thereaction was heated to 100° C., and stirred for 48 hours. The resultingwas cooled to room temperature to precipitate a solid, and the solid wascollected by filtering. The solid was washed by water and toluene, andthen sublimated at a temperature of 280° C. to obtain a yellow solid of0.69 g (yield=52%) as shown in Formula 5.

The yellow solid compound in Formula 5 was dissolved in dichloromethaneto form a solution having a concentration of 10⁻⁵ M, or evaporated toform a film having a thickness of 30 nm. The absorption-emission peaksof the film and the solution are tabulated in Table 1.

The spectra data of the compound in Formula 5 is shown as follows. ¹HNMR (400 MHz, CDCl₃): δ 9.01 (s, 1H), 8.79-8.70 (m, 5H), 8.33 (d, J=8.8Hz, 2H), 8.27-8.17 (m, 2H), 8.16-8.05 (m, 7H), 8.00 (d, J=7.2 Hz, 1H),7.79-7.68 (m, 6H). ¹³C NMR (125 MHz, CDCl₃): δ 141.9, 141.2, 139.6,137.6, 131.5, 131.0, 130.7, 130.2, 130.0, 129.8, 129.8, 129.7, 129.6,129.1, 129.0, 128.6, 127.7, 127.6, 127.5, 127.4, 127.4, 127.3, 127.3,127.3, 126.4, 126.3, 126.1, 125.3, 125.2, 125.0, 124.9, 124.7, 124.0,123.4, 123.3, 121.9. HRMS (m/z): [M⁺] calculated for C₄₀H₂₄, 504.1878.found, 504.1881. Element Analysis: calculated for C₄₀H₂₄: C, 95.21; H,4.79. found: C, 95.12; H, 4.78.

Example 3

(2-bromoethene-1,1,2-triyl)tribenzene (5.00 g, 14.9 mmol) was charged ina reaction bottle. The reaction bottle was then heated, vacuumed, andpurged with nitrogen. Dried tetrahydrofuran (50 mL) was added to thereaction bottle and stirred until (2-bromoethene-1,1,2-triyl)tribenzenewas dissolved, and the solution was cooled to −78° C. n-BuLi (15.00 mL,30.00 mmol, 2.0 M n-hexane solution) was dropwise added to the cooledsolution, and the reaction was stirred at −78° C. for 1 hour.Subsequently, B(OBu)₃ (11.00 mL, 40.8 mmol) was added to the reactionfor reaction for another 8 hours. The resulting mixture was acidified byHCl (2.0 M, 300 mL) for 3 hours. The acidified mixture was extracted byethyl acetate to collect the organic layer thereof. The organic layerwas dried by MgSO₄ and then condensed to precipitate a solid. The solidwas washed by n-hexane and filtered to obtain a white solid of 2.91 g(yield=65%) as shown in Formula 6.

The spectra data of the compound in Formula 6 is shown as follows. ¹HNMR (400 MHz, CDCl₃): δ 7.37-7.30 (m, 5H), 7.17-7.02 (m, 8H), 6.91-6.88(m, 2H), 4.08 (s, 2H). ¹³C NMR (100 MHz, CDCl₃): δ 153.2, 143.7, 142.3,142.0, 130.7, 129.8, 129.3, 128.6, 128.4, 128.2, 127.6, 127.0, 126.2.HRMS (m/z): [M⁺] calculated for C₂₀H₁₇BO₂, 300.1322. found, 300.1323.

The product in Formula 2 (1.00 g, 2.6 mmol), the compound in Formula 6(0.78 g, 2.6 mmol), potassium carbonate solution (2.0 M, 6.50 mL), anddried toluene (27 mL) were charged in a two-necked bottle. Thetwo-necked bottle was deoxygenated and purged with nitrogen, and themixture in the bottle was stirred at 60° C. until it was totallydissolved. The nitrogen pressure of the bottle was increased, andPd(PPh₃)₄ (0.15 g, 0.1 mmol) was rapidly added into the bottle. Thereaction was heated to 100° C., and stirred for 48 hours. The resultingwas filtered to remove metal, and then condensed to remove the solventto obtain a solid. The solid was washed by ethyl ether, filtered, andthen sublimated at a temperature of 290° C. to obtain a pale yellowsolid of 0.72 g (yield=50%) as shown in Formula 7.

The compound in Formula 7 was dissolved in dichloromethane to form asolution having a concentration of 10⁻⁵M, or evaporated to form a filmhaving a thickness of 30 nm. The absorption-emission peaks of the filmand the solution are tabulated in Table 1.

The spectra data of the compound in Formula 7 is shown as follows. ¹HNMR (400 MHz, CDCl₃): δ 8.65-8.54 (m, 5H), 8.32 (s, 1H), 7.68-7.63 (m,4H), 7.57-7.50 (m, 3H), 7.32-7.26 (m, 3H), 7.23-7.04 (m, 14H). ¹³C NMR(125 MHz, CDCl₃): δ 144.1, 144.0, 143.7, 143.6, 141.3, 140.9, 140.2,139.8, 131.6, 131.4, 131.3, 131.0, 130.4, 129.9, 129.9, 129.7, 129.7,129.6, 128.7, 128.3, 127.9, 127.7, 127.7, 127.2, 127.2, 127.1, 126.9,126.7, 126.5, 126.5, 126.3, 125.5, 123.6, 123.6, 123.3, 121.6. HRMS(m/z): [M⁺] calculated for C₄₄H₃₀, 558.2348. found, 558.2349. ElementalAnalysis: calculated for C₄₄H₃₀: C, 94.59; H, 5.41. found: C, 94.60; H,5.42.

Example 4

(2-bromoethene-1,1-diyl)dibenzene (2.00 g, 7.7 mmol) was charged in areaction bottle. The reaction bottle was then heated, vacuumed, andpurged with nitrogen. Dried tetrahydrofuran (30 mL) was added to thereaction bottle and stirred until (2-bromoethene-1,1-diyl)dibenzene wasdissolved, and the solution was cooled to −78° C. n-BuLi (4.64 mL, 11.6mmol, 2.5 M n-hexane solution) was dropwise added to the cooledsolution, and the reaction was stirred at −78° C. for 1 hour.Subsequently, B(OBu)₃ (1.32 mL, 11.6 mmol) was added to the reaction forreaction for another 8 hours. The resulting mixture was acidified by HCl(2.0 M, 300 mL) for 3 hours. The acidified mixture was extracted byethyl acetate to collect the organic layer thereof. The organic layerwas dried by MgSO₄ and then condensed to precipitate a solid. The solidwas washed by n-hexane and filtered to obtain a white solid of 1.21 g(yield=70%) as shown in Formula 8.

The product in Formula 2 (200 mg, 0.52 mmol), the compound in Formula 8(128.6 mg, 0.57 mmol), potassium carbonate solution (2.0 M, 6.50 mL),and dried toluene (27 mL) were charged in a two-necked bottle. Thetwo-necked bottle was deoxygenated and purged with nitrogen, and themixture in the bottle was stirred at 60° C. until it was totallydissolved. The nitrogen pressure of the bottle was increased, andPd(PPh₃)₄ (57.8 mg, 0.05 mmol) was rapidly added into the bottle. Thereaction was heated to 100° C., and stirred for 48 hours. The resultingwas filtered to remove metal, and then condensed to remove the solventto obtain a solid. The solid was washed by ethyl ether, filtered, andthen sublimated at a temperature of 250° C. to obtain a white solid of139 mg (yield=55%) as shown in Formula 9.

The spectra data of the compound in Formula 9 is shown as follows. ¹HNMR (400 MHz, CDCl₃) δ 8.66-8.58 (m, 5H), 8.46 (d, J=1.6 Hz, 1H),7.71-7.61 (m, 5H), 7.55 (d, J=7.6, 1H), 7.47-7.43 (m, 4H), 7.39-7.31 (m,8H), 7.16 (d, J=7.6, 1H), 7.09 (s, 1H).

Example 5

9H-carbazole (1.67 g, 10.0 mmol), 1-bromo-4-iodobenzene (3.39 g, 12.0mmol), copper (I) iodide (0.19 g, 1.0 mmol), L-proline (0.23 g, 2.0mmol), and potassium carbonate (2.76 g, 20.0 mmol) were charged in atwo-necked bottle. The bottle was then vacuumed and purged withnitrogen. Dimethyl sulfoxide (25 mL) was added to the bottle. Themixture in the bottle was heated to 90° C. and stirred for 48 hours. Theresulting was extracted by dichloromethane and water. The organic layerof the extraction was dried by MgSO₄, condensed, and purified bychromatography with an eluent of n-hexane to obtain a white solid of2.09 g (yield=65%) as shown in Formula 10.

The spectra data of the compound in Formula 10 is shown as follows. ¹HNMR (400 MHz, CDCl₃): δ 8.12 (d, J=8.0 Hz, 2H), 7.71 (d, J=8.4 Hz, 2H),7.44 (d, J=8.4 Hz, 2H), 7.40 (t, J=7.6 Hz, 2H), 7.35 (d, J=8.0 Hz, 2H),7.28 (t, J=7.2 Hz, 2H). ¹³C NMR (100 MHz, CDCl₃): δ 140.6, 136.8, 133.1,128.7, 126.0, 123.5, 120.8, 120.4, 120.2, 109.5. HRMS (m/z): [M⁺]calculated for C₁₈H₁₂BrN, 321.0153. found, 321.0145.

The compound in Formula 10 (1.60 g, 5.0 mmol) was charged in a reactionbottle. The reaction bottle was then heated, vacuumed, and purged withnitrogen. Dried tetrahydrofuran (80 mL) was added to the reaction bottleand stirred until the compound in Formula 10 was totally dissolved, andthe solution was cooled to −78° C. n-BuLi (2.40 mL, 6.0 mmol, 2.5 Mn-hexane solution) was dropwise added to the cooled solution, and thereaction was stirred at −78° C. for 1 hour. Subsequently, B(OCH₃)₃ (0.86mL, 7.5 mmol) was added to the reaction for reaction for another 8hours. The resulting was extracted by ethyl ether and water. The organiclayer of the extraction was dried by MgSO₄, and condensed to obtain asolid.

The solid was charged in a reaction bottle. Benzene (15 mL) and pinacol(1.20 g, 10.2 mmol) were added to the reaction bottle. The mixture washeated to 120° C. to reflux for 2 hours. The resulting was directlycondensed, and recrystallized by n-hexane and chloroform to obtain awhite solid of 1.04 g (yield=57%) as shown in Formula 11.

The spectra data of the compound in Formula 11 is shown as follows. ¹HNMR (400 MHz, CDCl₃): δ 8.12 (d, J=7.6 Hz, 2H), 8.03 (d, J=8.4 Hz, 2H),7.58 (d, J=8.0 Hz, 2H), 7.42 (t, J=8.0 Hz, 2H), 7.38 (d, J=7.6 Hz, 2H),7.27 (t, J=7.6 Hz, 2H), 1.38 (s, 12H). ¹³C NMR (100 MHz, CDCl₃) δ 140.6,140.3, 136.4, 126.1, 125.9, 125.5, 120.3, 120.0, 109.8, 109.7, 84.1,24.9. HRMS (m/z): [M⁺] calculated for C₂₄H₂₄BNO₂, 369.1900. found,369.1897.

The product in Formula 2 (1.04 g, 2.7 mmol), the compound in Formula 11(1.00 g, 2.7 mmol), potassium carbonate solution (2.0 M, 6.70 mL), anddried toluene (28 mL) were charged in a two-necked bottle. Thetwo-necked bottle was deoxygenated and purged with nitrogen, and themixture in the bottle was stirred at 60° C. until it was totallydissolved. The nitrogen pressure of the bottle was increased, andPd(PPh₃)₄ (0.16 g, 0.1 mmol) was rapidly added into the bottle. Thereaction was heated to 100° C., and stirred for 48 hours. The resultingwas filtered to remove metal, and then condensed to remove the solventto obtain a solid. The solid was washed by ethyl ether, filtered, andthen sublimated at a temperature of 290° C. to obtain a white solid of0.94 g (yield=63%) as shown in Formula 12.

The compound in Formula 12 was dissolved in dichloromethane to form asolution having a concentration of 10⁻⁵M, or evaporated to form a filmhaving a thickness of 30 nm. The absorption-emission peaks of the filmand the solution are tabulated in Table 1.

The spectra data of the compound in Formula 12 is shown as follows. ¹HNMR (400 MHz, CDCl₃): δ 8.93 (s, 1H), 8.79-8.66 (m, 5H), 8.16 (d, J=7.6Hz, 2H), 8.10 (s, 1H), 7.98 (d, J=8.4 Hz, 1H), 7.93 (d, J=8.0 Hz, 2H),7.84 (d, J=7.6 Hz, 1H), 7.75-7.64 (m, 8H), 7.51 (d, J=8.0 Hz, 2H), 7.43(t, J=8.0 Hz, 2H), 7.30 (t, J=7.6 Hz, 2H). ¹³C NMR (125 MHz, CDCl₃): δ141.9, 141.0, 140.8, 140.1, 139.6, 137.0, 130.1, 130.0, 129.8, 129.7,129.5, 129.1, 128.6, 127.4, 127.3, 127.3, 127.2, 126.7, 126.3, 126.3,126.3, 126.0, 123.9, 123.4, 123.4, 123.3, 123.3, 121.8, 120.3, 120.0,109.8. HRMS (m/z): [M⁺] calculated for C₄₂H₂₇N, 545.2143. found,545.2153. Elementary Analysis calculated for C₄₂H₂₇N: C, 92.45; H, 4.99;N, 2.57. found: C, 92.39; H, 5.03; N, 2.56.

Example 6

9,10-dibromoanthracene (4.00 g, 11.9 mmol), phenylboronic acid (1.60 g,13.1 mmol), potassium carbonate solution (2.0 M, 24.00 mL), and driedtoluene (70 mL) were charged in a two-necked bottle. The two-neckedbottle was deoxygenated and purged with nitrogen, and the mixture in thebottle was stirred at 60° C. until it was totally dissolved. Thenitrogen pressure of the bottle was increased, and Pd(PPh₃)₄ (0.68 g,0.6 mmol) was rapidly added into the bottle. The reaction was heated to100° C., and stirred for 48 hours. The resulting was filtered to removemetal. The filtrate was extracted by the dichloromethane. The organiclayer of the extraction was dried by MgSO₄, condensed, and purified bychromatography with an eluent of n-hexane to obtain a yellow solid of2.08 g (yield=52%) as shown in Formula 13.

The spectra data of the compound in Formula 13 is shown as follows. ¹HNMR (400 MHz, CDCl₃): δ 8.61 (d, J=8.8 Hz, 2H), 7.65 (d, J=8.8 Hz, 2H),7.63-7.55 (m, 5H), 7.42-7.38 (m, 4H). ¹³C NMR (100 MHz, CDCl₃): δ 138.4,137.8, 131.1, 131.0, 130.2, 128.4, 127.8, 127.7, 127.4, 126.9, 125.5,122.7. HRMS (m/z): [M⁺] calculated for C₂₀H₁₃Br, 332.0201. found,332.0202.

The compound in Formula 13 (1.50 g, 4.5 mmol) was charged in a reactionbottle. The reaction bottle was then heated, vacuumed, and purged withnitrogen. Dried tetrahydrofuran (24 mL) was added to the reaction bottleand stirred until the compound in Formula 13 was dissolved, and thesolution was cooled to −78° C. n-BuLi (2.16 mL, 5.4 mmol, 2.5 M n-hexanesolution) was dropwise added to the cooled solution, and the reactionwas stirred at −78° C. for 1 hour. Subsequently, B(OCH₃)₃ (0.78 mL, 6.8mmol) was added to the reaction for reaction for another 8 hours. Theresulting was extracted by ethyl ether and water. The organic layer ofthe extraction was dried by MgSO₄, and condensed to obtain a solid.

The solid was charged in a reaction bottle. Benzene (15 mL) and pinacol(1.07 g, 9.1 mmol) were added to the reaction bottle. The mixture washeated to 120° C. to reflux for 2 hours. The resulting was directlycondensed, and purified by chromatography with an eluent of ethylacetate/n-hexane (1:40) to obtain a yellow solid of 1.00 g (yield=58%)as shown in Formula 14.

The spectra data of the compound in Formula 14 is shown as follows. ¹HNMR (400 MHz, CDCl₃): δ 8.42 (d, J=8.8 Hz, 2H), 7.61 (d, J=8.8 Hz, 2H),7.57-7.48 (m, 3H), 7.45 (t, J=7.6 Hz, 2H), 7.37 (d, J=6.4 Hz, 2H), 7.29(t, J=7.6 Hz, 2H), 1.59 (s, 12H). ¹³C NMR (100 MHz, CDCl₃): δ 139.5,139.1, 135.3, 131.0, 129.7, 128.3, 128.3, 127.4, 125.4, 124.8, 84.5,25.2. HRMS (m/z): [M⁺] calculated for C₂₆H₂₅BO₂, 380.1948. found,380.1956.

The product in Formula 2 (1.21 g, 3.2 mmol), the compound in Formula 14(1.20 g, 3.2 mmol), potassium carbonate solution (2.0 M, 7.8 mL), anddried toluene (33 mL) were charged in a two-necked bottle. Thetwo-necked bottle was deoxygenated and purged with nitrogen, and themixture in the bottle was stirred at 60° C. until it was totallydissolved. The nitrogen pressure of the bottle was increased, andPd(PPh₃)₄ (0.18 g, 0.2 mmol) was rapidly added into the bottle. Thereaction was heated to 100° C., and stirred for 48 hours. The resultingwas cooled to precipitate a solid. The solid was collected by filtering,washed by water and methanol, and sublimated at 260° C. to obtain ayellow solid of 0.97 g (yield=55%) as shown in Formula 15.

The compound in Formula 15 was dissolved in dichloromethane to form asolution having a concentration of 10⁻⁵M, or evaporated to form a filmhaving a thickness of 50 nm. The absorption-emission peaks of the filmand the solution are tabulated in Table 1.

The spectra data of the compound in Formula 15 is shown as follows. ¹HNMR (400 MHz, CDCl₃): δ 8.95 (s, 1H), 8.72-8.64 (m, 5H), 8.03-7.97 (m,3H), 7.84 (dd, J=7.2, 2.0 Hz, 2H), 7.77 (t, J=8.0 Hz, 1H), 7.72 (dd,J=7.2, 2.0 Hz, 2H), 7.67-7.49 (m, 10H), 7.39-7.33 (m, 4H). ¹³C NMR (125MHz, CDCl₃): δ 141.1, 140.2, 140.1, 139.8, 139.3, 139.0, 137.3, 136.9,131.3, 130.6, 130.1, 130.0, 129.9, 129.8, 129.7, 129.5, 129.1, 129.0,128.4, 127.8, 127.5, 127.4, 127.3, 127.2, 127.0, 127.0, 126.4, 126.3,126.1, 125.2, 125.1, 124.0, 123.6, 123.4, 123.3, 121.8. HRMS (m/z): [M⁺]calculated for C₄₄H₂₈, 556.2191. found, 556.2196. Elementary Analysis:calculated for C₄₄H₂₈: C, 94.93; H, 5.07. found: C, 94.71; H, 5.12.

TABLE 1 Solution type Film type Absorption peaks (nm, molar EmissionAbsorption Emission extinction coefficient (10⁴ M⁻¹ cm⁻¹)) peak (nm)peak (nm) peak (nm) Product in 232 (12.17), 270 (12.96), 310 (5.37) 368280, 324 408 Formula 1 Formula 5 274(11.80), 315 (35.60), 332 (38.50),383, 400 277, 353 464 345 (45.40) Formula 7 274 (14.06), 304 (6.72) 383,401 271, 321 467 Formula 9 271 (8.72), 304 (4.96) 379 Not measured Notmeasured Formula 12 266 (23.07), 293 (12.78), 305 (9.95) 375, 394 261,296, 319 388 Formula 15 261 (221.8), 306 (3.33), 357 (1.36), 412, 431369, 361, 381, 403 429, 444 375 (2.10), 395 (1.97)

As tabulated in Table 2, the solutions of the white solid product inFormula 1, the yellow solid compound in Formula 5, the pale yellow solidcompound in Formula 7, the white solid compound in Formula 9, the whitesolid compound in Formula 12, and the yellow solid compound in Formula15 were measured by cyclic voltammetry, respectively, to obtain theirHOMO, LUMO, and energy gap between the HOMO and LUMO.

TABLE 2 Product in For- For- For- Formula Formula Formula 1 mula 5 mula7 mula 9 12 15 HOMO (eV) 5.90 5.66 5.74 5.90 5.66 5.56 LUMO (eV) 2.092.32 2.28 2.18 2.09 2.41 Energy 3.81 3.34 3.46 3.72 3.57 3.15 gap (eV)

Table 2 indicates that the triphenylene based aromatic compounds in theinvention have lower HOMO, thereby benefiting the hole transporting. Assuch, the light emitting layer utilizing the triphenylene based aromaticcompounds in the invention may eliminate the so-called hole transportinglayer. Meanwhile, the triphenylene based aromatic compounds in theinvention may serve as the hole transporting layer integrated with otherconventional light emitting layers to further improve deviceperformance.

Example 7

The glass transition temperature (Tg), the crystal temperature (Tc), andthe melting temperature (Tm) of the product in Formula 1, the compoundin Formula 5, the compound in Formula 7, the compound in Formula 12, thecompound in Formula 15, and the compound in Formula 16 (synthesized inJ. Phys. Chem. C 113, 7405 (2009)) were analyzed by a DSC with a risingtemperature rate of 10° C./minute under nitrogen, respectively. Thethermal analysis data of those compounds are tabulated in Table 3.

TABLE 3 Tg (° C.) Tc (° C.) Tm (° C.) Product in Formula 1 127 210 275Formula 5 116 None None Formula 7 108 None 220 Formula 12 118 None 223Formula 15 135 None 285 Formula 16 None None 393

As shown in Table 3, although both of the product in Formula 1 and thecompound in Formula 16 have a benzene center and two triphenylenylsubstituents, the meta-substituted product in Formula 1 has betterthermal stability than the para-substituted compound in Formula 16. Thecompound in Formula 16 does not have Tg. Thus, it is easily crystallizedby heating. In addition, the compound in Formula 16 has higher Tm. Thus,increasing process difficulty due to be easily solidified on the wall ofthe evaporation boat while being evaporated. Accordingly, themeta-substituted compound in the invention has better thermal stabilitythan the conventional para-substituted compound.

Example 8

In one example, the ITO was served as an anode, 50 nm of TCTA served asa hole transporting layer, 30 nm of the host material (such as theproduct in Formula 1, the compound in Formula 5, the compound in Formula7, the compound in Formula 12, and the compound in Formula 15) served asa light emitting layer, 10 nm of the BCP served as a hole blockinglayer, 30 nm of Alq₃ served as a electron transporting layer, 1 nm ofLiF served as a electron injecting layer, and 100 nm of Al served as acathode were sequentially formed on the ITO anode. In another example,the ITO was served as an anode, 50 nm of NPB served as a holetransporting layer, 30 nm of the host material (such as the compound inFormula 16) served as a light emitting layer, 10 nm of the BCP served asa hole blocking layer, 30 nm of Alq₃ served as a electron transportinglayer, 55 nm of magnesium silver alloy served as a electron injectinglayer, and 100 nm of Ag served as a cathode were sequentially formed onthe ITO anode. The external quantum efficiency (E.Q.E.), the currentefficiency (C. E.), the power efficiency (P. E.), the maximumbrightness, the driving voltage, and the CIE coordination of the devicesare tabulated in Table 4.

TABLE 4 Light Max Driving emitting C.E. P.E. brightness voltage CIElayer E.Q.E. (%) (V) (cd/A) (lm/W) (cd/m²) (V) (V) coordination Formula16  2.5 (8.0) 3.39 1.41 15285 (20.5) 4.0 (0.15, 0.16) Product in 2.65(8.5) 0.89 0.34  1939 (15.0) 5.8 (0.16, 0.66) Formula 1 Formula 5 4.35(9.5) 4.54 1.80 22100 (19.0) 4.7 (0.15, 0.12) Formula 7 2.49 (9.0) 4.311.58 10310 (15.5) 6.2 (0.17, 0.24)) Formula 12 0.93 (7.5) 0.51 0.22 1627 (16.0) 6.0 (0.16, 0.09) Formula 15 3.96 (8.0) 2.41 1.07  6011(13.5) 4.6 (0.15, 0.07)

As shown in Table 4, the best device luminescence performance isachieved by the light emitting layer adopting the compound in Formula 5.

Example 9

Example 9 was similar to Example 8, except that the light emitting layerin Example 9 was further doped with 3% of BCzVBi. The external quantumefficiency (E.Q.E.), the current efficiency (C. E.), the powerefficiency (P. E.), the maximum brightness, the driving voltage, and theCIE coordination of the devices are tabulated in Table 5.

TABLE 5 Host material in the Light Driving emitting E.Q.E. (%) C.E. P.E.Max brightness voltage CIE layer (V) (cd/A) (lm/W) (cd/m²) (V) (V)coordination Formula 16 4.93 (6.0) 6.22 3.74 17797 (17.0) 4.2 (0.15,0.16) Product in 6.06 (4.5) 8.4 5.88 33800 (16.0) 4.5 (0.14, 0.18)Formula 1 Formula 5 9.17 (9.5) 12.99 6.23 63362 (20.0) 4.2 (0.14, 0.19)Formula 7 8.33 (7.0) 8.94 4.73 23600 (18.0) 5.2 (0.14, 0.12) Formula 125.35 (7.5) 6.28 2.80 25012 (17.5) 4.4 (0.14, 0.14) Formula 15 7.58 (8.5)9.41 3.61 36244 (16.5) 5.5 (0.15, 0.15)

As shown in Table 5, the dopant BCzVBi may further improve deviceluminescence performance. In addition, the meta-substituted compound ismore preferable to be the host material in the light emitting layer thanthe conventional para-substituted compound. For further reference, seecomparison of the compound in Formula 16 and the product in Formula 1.

While the invention has been described by way of example and in terms ofthe preferred embodiments, it is to be understood that the invention isnot limited to the disclosed embodiments. To the contrary, it isintended to cover various modifications and similar arrangements (aswould be apparent to those skilled in the art). Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

1. A triphenylene based aromatic compound, having a general formula:

wherein Ar₁ is a triphenylenyl group, and Ar₂ is a pyrenyl group.
 2. Thetriphenylene based aromatic compound as claimed in claim 1, wherein Ar₁,Ar₂, and a benzene center independently have one or more substituentsselected from the group consisting of hydrogen, halogen, aryl,halogen-substituted aryl, halogen-substituted aryl alkyl,haloalkyl-substituted aryl, haloalkyl-substituted aryl alkyl,aryl-substituted C₁₋₂₀ alkyl, electron donating group, electronwithdrawing group, and heterocyclic-substituents.
 3. The triphenylenebased aromatic compound as claimed in claim 1, having a general formula:


4. An organic light emitting diode, comprising: an anode; a cathode; andan organic layer disposed between the anode and the cathode, wherein theorganic layer comprises the triphenylene based aromatic compound asclaimed in claim
 1. 5. The organic light emitting diode as claimed inclaim 4, wherein the organic layer comprises a light emitting layer, ahole transporting layer, or combinations thereof.